The 10 worst PC viruses of 2004

Anti-virus specialist Panda Software has named the Downloader.GK Trojan as the virus that caused the most amount of damage to computers across the world in 2004.

Downloader.GK is a virus that infects machines when unsuspecting users visit certain web pages and accidentally instal an ActiveX control, which in turn secretly runs two adware programmes on the computers it infects.

Experts say that the threat from these viruses will continue to cause major headaches for people in this 2005 too.

More than 14 per cent of all attacks on computers detected by Panda's ActiveScan were due to Downloader.GK.

The top ten threats identified by Panda include:

1. Downloader.GK (14 per cent)

2. Netsky.P (6.92 per cent)

3. Sasser.ftp (4.97 per cent)

4. Gaobot.gen (4.31 per cent)

5. Mhtredir.gen (4.22 per cent)

6. Netsky.D (3.98 per cent)

7. Downloader.L (3.56 per cent)

8. Qhost.gen (3.48 per cent)

9. Netsky.B (3.45 per cent)

10. StartPage.FH (3.34 per cent)

Three of the Top Ten ranking are members of the Netsky family, (the P,B and D variants). The three share a number of characteristics, and as with many worms, they all spread via e-mail in messages with variable characteristics.